Means for finishing workpieces of



July 6, 1954 H. D. COE, JR., ET AL Original Filed Nov. 26, 1948 Fig.l.I8 20 I6 Fig.3.

3'1 43 as as a as T 26 2: 28 22 23 WITNESSES: INVENTORS Hurry D.Ooe,Jr.cnd

Josaph B.Dym.

M i C w. 2 ATTORNEY Reissued July 6, 1954 MEANS FOR FINISHING WORKPIECESOF IRREGULAR SHAPES Harry D. Ooe, Jr., and Joseph B. Dym, Pittsburgh,Pa.; said Dym assignor to said Coe, Jr.

Original No. 2,575,656, dat Serial No. 62,102, Nevem ed November 20,1951, her 26, 194.8. Application for reissue October 22, 1952, SerialNo.

7 Claims. 01. 51 141 Matter enclosed in heavy brackets E appears in theoriginai patent but forms no part of this reissue specification;

Our invention relates to [method and] means for grinding, sanding,polishing or otherwise finishing irregularly shaped surfaces ofworkpieces such as turbine blades, hardware, streamlined applianceparts, cams, etc.

In the manufacture of irregularly shaped bodies it has been a problem toaccurately obtain the desired or theoretically correct surface. Forinstance, with turbine blades of irregular contour, the conventionalpractice has been to forge or cast the material as close as possible tothe desired shape and then improve the finish and correct the shape byhand polishing. The blades are alternately held against an abrasivepolishing wheel and checked against profile gages at three points untilthe desired shape is obtained. This method is not only time consuming,but the attainable accuracy depends only upon the skill and judgment ofthe operator.

It is an object of our invention to provide methods and means thataiford bringing irregular bodies into the desired shape with any desireddegree of accuracy and in considerably less time than heretoforerequired.

Another object of the invention is to greatly reduce the skill requiredfor obtaining accurately finished surfaces and to render the accuracyuniform over the whole finished surface. These and other objects of ourinvention will be apparent from the following description.

In accordance with the [invented method] invention we provide a rigidform block or matrix with an irregular matrix suface that substantiallymatches the irregular surface to be finished, and we run an abrasivebelt with its smooth side over the form block while keeping the beltslack. We further hold the workpiece to be finished on the abrasive sideof the running belt against the matrix surface of the form block sothat, due to the slackness of the belt, the belt adapts itself to theirregular matrix surface. In this manner, the workpiece can beaccurately finished merely by holding or forcing it toward the formpiecewithout requiring special skill and within a period of only a smallfraction of the time necessary for the above-mentioned conventionalmethod.

If the workpiece surface is deeply concave, the belt is run directlyover a correspondingly convex form block with the abrasive side out andso guided that it approaches and leaves the block approximatelytangential to the surface at the first and last points of contactrespectively. If

the surface of the form block or workpiece is sufficiently conical togive the belt the tendency to matter printed in italics indicates theadditions made by reissue.

run off the form block, an auxiliary form block of similar shape isprovided in reversed relation to the active form block to correct thistendency.

1f the surface to be finished is convex or a combination of concave andconvex, the abrasive belt is run with no initial, or no appreciabletension and enough slack to adapt itself to the concave matrix surfacearea of the form block. The larger degree of slack thus required maymake it difficult to drive the abrasive belt with belt wheels in theordinary manner. However, the belt can then be forced against the beltwheels to secure the necessary traction. One way of doing this is to usevacuum on the belt wheels to suck and hold the running abrasive beltagainst the wheels. This vacuum method may lead to objectionable noise.According to another and preferred procedure, we run a drive belttogether with the abrasive belt over the wheels and keep both belts inface-to-face contact over a sufficient length to secure the neededtraction so that a portion of the abrasive belt can then run free andslack.

The above-mentioned [methods] invention as well as examples of devicessuitable for [performing] carrying out these [methods] inventions willbe understood from the following description of the embodimentsillustrated in the drawing, in which:

Figure 1 shows diagrammatically a machine for finishing turbine bladesor other workpieces with deeply concave surfaces,

Fig. 2 shows a top view of the workpiece, abrasive belt and form blockof the same machine; and

Fig. 3 is a diagrammatic illustration of another machine especiallydesigned for finishing [convex] a concave or a slightly convex surface.

The machine illustrated by Figures 1 and 2 is equipped with a drivestandl for a belt driving wheel 2 whose shaft 3 has bearings rigidly mountedon the stand. The running direction of the driving wheel 2 is indicatedby an arrow 4. A backstand 5 of the machine is equipped with an idlerwheel 6 whose shaft 1 is journalled in a link structure 8 pivoted at 9to the stand 5. The link structure 8 is biased by a weight l0 and tendsto move the idle wheel away from the driving wheel, thus maintaining theabrasive belt I! in sufiiciently taut condition to secure the necessarytraction while permitting the belt to yield and become slack at theplace of the form block described presently.

A workstand i2 iocated between a drivestand and backstand carries a beltguiding wheel it and a form block or matrix 14. The form block isrigidly attached to the workstand. Its matrix surface has an irregularshape in order to permit finishing the correspondingly irregular surfaceof a turbine blade or other workpiece in accordance with theabove-described method. The machine, according to Fig. l is especiallydesigned for finishing workpieces with deeply concave surfaces. In theillustrated embodiment, this surface is assumed to be generally conicalso that the form block l4 may cause the abrasive belt i l to run off thematrix surface. In order to prevent this, an auxiliary or compensatingform block is also mounted on the workstand. The compensating form blockhas about the same shape as the main form block l4, but is arranged inthe reverse direction, i. e., the tapering side of its surface points tothe other side of the belt and hence compensates for the tendency of thebelt to run off the form block I4.

Two guides l6 and H are provided in order to facilitate placing theworkpiece [8 in the proper position on the abrasive side of the belt.When the belt is running and the workpiece is held on the abrasive beltside against the matrix surface of the form block M, the belt assumessufficient slackness between the driving wheel and the form block topermit the belt portion at the matrix surface to adapt itself to thatsurface. As a result, the workpiece surface is finished with the desiredaccurate shape without requiring special skill and within a period oftime much shorter than otherwise required. A water spray nozzle isdenoted by A9 and an arrow indicates the feeding direction for theworkpiece [8. The arrangement of the form block I4 is preferably suchthat the belt I l approaches and leaves the block approximatelytangential to the matrix and workpiece surface at the first and lastpoint of contact respectively.

The machine illustrated in Fig. 3 has a drivestand 2| for the drivingwheel 22. As in the machine of Fig. 1, the bearings for the wheel shaft23 are rigidly mounted on the stand. The driving direction of the wheelis indicated by an arrow 24. A backstand 25 carries an idler wheel 23.The shaft 27 is journalled in a structure 28 that is pivoted at 29 tothe stand 25 and biased by a weight 3%. The abrasive belt 3i whichextends around the drive wheel 22 and idler wheel 26 passes over thematrix surface of a convex form block 34, which is mounted on aworkstand 32. The workstand 32 is also equipped with guides 35 and 3'!for the workpiece 38 and with a water spray nozzle 35. In order topermit the belt to adapt itself closely to the concave matrix surfacewhile running over the form block, a larger amount of yielding orslackness is required than with convex matrix surface. Consequently, thetraction of the driving wheel may become insufficient to pull the beltover the form block when the workpiece is fed against the block. Inorder to secure the necessary traction, the machine according to Fig. 3is equipped with an auxiliary rubber belt 40. the abrasive belt, but hasgreater length so that it lies in face-to-face relation with theabrasive belt on only one side of the wheels but is spaced from theabrasive belt at the other side. In order to maintain the proper spacingand for keeping the auxiliary traction belt in taut condition, apressure roller 4| engages the belt 49. The roller 4| is journalled onan arm 42 pivoted at 43 to the workstand 32 and secured in the desiredposition by means of an adjusting screw 44.

When the machine is in operation and the This belt is endlesslikeworkpiece 38 held on the abrasive side of belt 3| against the formblock 34, the belt portion between the driving wheel 22 and the formblock 34 can run with any suitable degree of slackness without reducingthe traction below the required amount.

Methods and means, according to the invention, are applicable withadvantage for the finishing of a large variety of irregular surfaces, i.e., of surfaces that are neither plane nor straight cylindrical orstraight conical and hence cannot readily be shaped by conventionalturning, shaping and grinding devices. Aside from the fact that theinvention secures a high accuracy and requiresless skill, thefabricating method used for bringing the workpiece surface intoapproximately the desired shape before finishing need not be so closelycontrolled as is necessary in the conventional procedure, thus loweringthe amount of rejects and further reducing the finishing cost. Forexample, in machines built and operated according to the invention forfinishing gas turbine blades, the overall savings afforded by theinvention in comparison with the conventional methods amounted toapproximately The invention also affords a very simple method of formingand redressing the matrix blocks. For such purposes, it is merelynecessary to reverse the belt so that its abrasive side runs over thematrix block to be finished or redressed, and to hold a master workpieceon the smooth belt side against the matrix block.

It will be obvious to those skilled in the art after a study of thepresent disclosure, that devices according to the invention can bemodified as respects various design details and components withoutdeparting from the essence and features of our invention and Within thescope of the claims annexed hereto.

We claim as our invention:

[1. A device for finishing a workpiece of irregular shape, comprisingtwo initially spaced belt wheels, an endless abrasive belt having asmooth inner surface and an abrasive outer surface and extending aroundsaid two wheels, an endless drive belt extending around said two wheels,said drive belt having a portion extending from one to the other wheelin face-to-face engagement with said abrasive belt and having anotherportion spaced from said abrasive belt, and a form block disposedbetween said wheels ata place where said driving belt is spaced fromsaid abrasive belt, said form block having a matrix surfacesubstantially matching the surface to be finished and engageable by saidinner surface of said abrasive belt when a workpiece is held on theouter side of said abrasive belt against said block] [2. A device forfinishing a workpiece of irregular shape, comprising two mutually spacedbelt wheels, an endless abrasive belt having asmooth inner surface andan abrasive outer sur face and surrounding said two wheels, an endlessdrive belt having larger length than said abrasive belt and surroundingsaid wheels and said abrasive belt, tautening means engaging said drivebelt to maintain it spaced from said abrasive belt at one side of saidwheels and in contact with said abrasive surface of the other side ofsaid wheels, a form block having a matrix surface substantially matchingthe surface to be finished and being engageable by said abrasive surfaceof said abrasive belt and disposed at a place Where said drive belt isspaced from said abrasive belt] [3. In a device according to claim 2,one of said wheels having a drive shaft and a stationary axis, saidother wheel having an idler shaft movable toward and away from saiddrive shaft, and biasing means connected with said idler shaft forbiasing it away from said drive shaft] [4. A device for finishing aworkpiece of irregular shape, comprising two mutually spaced beltwheels, an endless abrasive belt having a smooth inner surface and anabrasive outer surface and surrounding said two wheels, an endless drivebelt having larger length than said abrasive belt and surrounding saidwheels and said abrasive belt, tautening means engaging said drive beltto maintain it spaced from said abrasive belt at one side of said wheelsand in contact with said abrasive surface of the other side of saidwheels, and a supporting block having a surface engaged by the innerside of said abrasive belt and being disposed within said abrasive beltat the belt side where said drive belt is spaced from said abrasivebelt] 5. A device for finishing a workpiece of irregular shape,comprising two wheels, mounting means for each of said wheels formounting said wheels spaced relationship, each wheel rotatable about itsaxis relative to its mounting means, means for supporting the mountingmeans for one wheel movable relative to the other mounting means so thatthe axis of said one wheel may be moved relative tothe axis of the otherwheel, an endless abrasive belt having an abrasive surface and extendingaround said two wheels, an endless drive belt having a portion extendingfrom one to the other wheel in face-to-face en- 7 tween said wheels at aplace where said driving belt is spaced from said abrasive belt, saidform block having a matrix surface substantially conforming with thesurface tobe finished in male female relationship and engageab-le by onesurface of said abrasive belt when a workpiece is held against the othersurface of said abrasive belt.

6. A device for finishing a workpiece of irregular shape, comprising twobelt wheels, mounting means for each of said wheels for mounting saidwheels mutually spaced, each rotatable about its axis relative to itsmounting means, an endlessabrasive belt having at least one abrasivesurface and surrounding said two wheels, an endless drive belt indriving engagement with said abrasive belt, said abrasive belt beingdisposed between. said drive belt and said wheels, tautening meansengaging said drive belt to maintain it spaced from said abrasive belton at least one side of said wheels and a form block having a matrixsurface substantially conforming with the surface to be finished in maleand female relationship and being engageab-le by said abrasive belt anddisposed at a piace where said drive belt is spaced from said abrasivebelt.

7. In a device according to claim 6, the mounting means of one of saidwheels having a drive shaft for said one wheel and a stationary axis,

the mounting means of said other wheel having an idler shaft movabletoward and away from said drive shaft, and biasing means connected -withsaid idler shaft for biasing it away from said drive shaft.

8. A device for finishing a workpiece of irregular shape, comprising twobelt wheels, mounting means for each of said wheels for mounting saidwheels in mutually spaced relationship, each wheel rotatable about itsaxis relative to its mounting means, an endless abrasive belt having atleast one abrasive surface and surrounding said two wheels, an endlessdrive belt in driving engagement with said abrasive belt, said abrasivebelt being disposed between said wheels and said drive belt, tauteningmeans engaging said drive belt to maintain it spaced from said abrasivebelt on at least one side of said wheels and a supporting block having asurface engaged by one surface of said abrasive belt and being disposedadjacent said abrasive belt on the side of said abrasive belt where saiddrive belt is spaced from said abrasive belt.

9. Apparatus for finishing the surface ofa workpiece of irregular shapecomprising in combination meansfor mounting said workpiece with saidsurface in grinding position, a first wheel adjacent said mountingmeans, a support for said first wheel for supporting said first wheelrotatable about its axis, mounting means for said support for mountingsaid support movable so that the axis about which said wheel rotates isdisplaceable, a second wheel adjacent said workpiece mounting means, asupport for said second wheel, an abrasive belt operatively engagingsaid wheels and adapted to move in grinding engagement with saidsurface, a second belt operatively engaging said abrasive belt over atleast portions of those portions of said abrasive belt which engage saidwheels, and holding said abrasive between said second belt and saidwheels, means cooperative with said second belt for driving saidabrasive belt, and means for positioning said first wheel by movement ofits support to obtain a predetermined amount of slackness in saidabrasive belt.

10. In combination a first wheel; a second wheel; a first support intowhich said first wheel is fournaled to rotate about its axis; a secondsupport into which said second wheel is :iournaled to rotate about itsaxis, mounting means for one of said supports for mounting said onesupport movable so as to displace the axis of the wheel mounted on saidone support; an abrasive belt in operative engagement with said wheels;a second belt in operative engagement with said abrasive belt over atleast portions of those portions of said abrasive belt which engage saidwheels and holding said abrasivebelt between said second belt and saidwheels; means cooperative with said second belt for driving saidabrasive belt; and means cooperative with said support mounting meansfor varying relatively the lengths of the sections of said second beltwhich extend between the regions of engagement of said second belt andsaid abrasive belt.

11. Apparatus for finishing the surface of a workpiece, said surfacehaving a high degree of curvature comprising in combination means formounting said workpiece in grinding position, a wheel, a support onwhich said wheel is fournaled to rotate about its axis, mounting meansfor said support for mounting said support movable so as to displacesaid axis, an abrasive belt, means for positioning said belt inoperative engagement 7 with said wheel and in continuous grindingengagement with said entire surface of said workpiece, a second beltoperatively engaging said abrasive belt over at least a portion of thatportion of said abrasive belt which engages said whleel and holding saidabrasive belt between said second belt and said wheel, means cooperat vewith said second belt for driving said abrasive belt and meanscooperative with said second belt for positioning said wheel by movementof its support with its axis so displaced as to obtain an amount ofslackness in said abrasive belt adequate to conform said abrasive beltwith said surface having a high degree of curvature.

References Cited in the file of this patent or the original patentUNITED STATES PATENTS Name Date Leach Dec. 24, 1895 Number Number Number15 128,321

